1. Field of the Invention
The present invention relates to a device for automatically exchanging tools between a spindle of machine tool and a tool magazine.
2. Technical Background
Productivity improvement is one of the basic requirements of a machining center. With an improvement in cutting efficiency being achieved in modern machining centers, there is a strong need for shortening the non-cutting time particularly for light alloy fabrication operations which generally require short cutting time. There is thus an important need for shortening the time required for exchanging the tools between machining steps, because such steps occupy almost 20 percent of the total machining cycle time. To date, various tool exchanger devices have been disclosed, for example, in referenced such as Japanese Utility Model, S61-42755 and JP, First Publication, S61-53182 and JP, First Publication, H5-16047.
Such a device typically performs the following steps: gripping a tool, a used bit which has completed its job, disposed in the spindle; removing the used tool from the tapered hole of the spindle; exchanging the position of the used tool disposed on a line of the extension of the spindle with another tool to be used in the same position; inserting the another tool in the spindle; and releasing the hold on the spindle so that the spindle can rotate and move into an operating position. However, such a device tries to improve the machining efficiency by speeding up the steps by using hydraulic or mechanical transmission systems.
The conventional device of this type suffered from the following problems.
(a) There is a large motion range (the path of travel made by the tool bits to be exchanged), and the improvement is limited basically by the acceleration achievable within the speed attained by the tool.
(b) For each motion of the steps, acceleration and deceleration periods are required, and a time lag is generated.
(c) Various mechanisms are required for performing the various steps, and the device becomes complex to make, thus increasing the chances of device breakdowns.